The use of equalizers in connection with particular transmission methods or standards, such as ISDN, Ethernet, DSL, is well-known. However, these transmission methods provide a continuous transmission of data or information items with the aid of the transmitted signals. However, in the case of so-called burst transmission, which is used, for example, in motor vehicles in connection with special digital interfaces, continuous transmission of data is not provided.
In particular, in automotive technology, the standards relating to fuel efficiency, minimizing pollutant emissions, and safety are becoming more and more stringent. A result of this is that larger and larger sets of data must be transmitted more and more rapidly between sensors or actuators and the control unit, the central controller. It has been shown that this is only possible by introducing new digital interfaces, with the aid of which high transmission rates may be transmitted rapidly and reliably. In this context, it should be taken into consideration that the transmission of data at higher rates requires that the digital data be modulated onto transmission frequencies higher than the frequencies that were used in the past for data transmission between sensor and control unit.
A secondary effect of the data transmission at a higher bit rate is that the modulated signals are, by far, more markedly distorted than is the case with transmission in lower frequency ranges. The distortion of the signals may lead to a significant increase in the bit error rate of the transmitted data.
In principle, these channel distortions may be compensated for by equalizers at the receiver. In this connection, adaptive filters adjust automatically to unknown or changing channel environments. These days, such adaptive equalizers are used in many areas of digital communications technology.
In the case of the data transmission via the new digital interfaces and data buses that are being introduced into automotive technology, new equalizer configurations, which are introduced below, allow both the error rates to be significantly reduced and the data transmission rates to be increased by a multiple. For use in the digital transmission systems in the automotive area, a number of changes in the equalizer design in comparison with the equalizer structures known from the literature and from practice, must be undertaken due to the peculiarities of data transmission in the automotive area.
In the medium term, the use of equalizers in high-bit-rate transmission systems is inevitable in automotive technology, since the alternatives, such as low transmission rates, shorter transmission lines or the use of highly accurate and, therefore, expensive components have significant disadvantages.
In automotive technology, digital interfaces conforming to the CAN standard, the SENT standard and the PSI5 standard are used, inter alia, in the power train and in the chassis region. PSI5 (PSI: peripheral sensor interface) constitutes a digital interface for sensors, which is based on a two-wire line as a current interface and is used for connecting remote sensors to electronic control units. In the case of these new digital transmission methods, the effects of the channel distortions are of particularly high significance for the PSI5 technology, since the consequences of the channel distortions limit the possible line lengths, data transmission rates and bus topologies and produce bit error rates that are too high.